The practice of medicine has been revolutionized from the introduction of advanced technologies to clinical practice. Despite the introduction of novel technologies in minimally invasive surgery, there has been minimal change in the way surgeons are trained for minimally invasive surgery, which translates into less experience and guidance for the trainees. Because of the loss of natural sense of touch and visual feedback in minimally invasive surgical procedures, there is a compelling need for haptics and real-time graphics based surgical simulators for training a new generation surgeons. This proposal addresses four specific aims to address this challenge: 1) To experimentally measure and model in vivo soft-tissue responses during probing and dissection, 2) To experimentally measure soft-tissue response during in vivo cutting, and develop simulations for ex vivo cutting followed by in vivo cutting, 3) To experimentally measure and model soft-tissue response during electrocautery, and develop models to simulate the process for both ex vivo and in vivo measurements, and 4) To evaluate the benefits of simulator based training for two specific procedures, namely, incisional liver biopsy (to demonstrate probing and cutting) and laparoscopic cholecystectomy (to demonstrate dissection and electrocautery). Learning curves and task completion accuracy will be assessed for surgeons and residents in our real-time haptics and graphics based simulator and compared with operating room (OR) procedures and SurgicalSim (commercial surgical simulator). This proposal addresses the challenge of BRG by addressing problems in bioengineering and bringing biomechanical engineering, surgery, and computer graphics together to solve compelling surgical training problems. Clinically, development of the surgical training simulator will allow a more widespread use of surgical simulators for resident training (for both minimally invasive procedures using long instruments and direct palpation), whereby residents will be able to experience the correct soft-tissue response for surgical tasks. Also, such a system can be easily adapted to model any other organ or soft-tissue for which training is desired, once the basic paradigm is in place. Widespread availability of this state of the art training tool will help to elevate and equalize the level of basic surgical skills of residents in training by transcending national and resource barriers.